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Blackbody Radiation Calculator

Work out blackbody radiation instantly with clear inputs, formula shown and shareable results.

About Blackbody Radiation Calculator

A black body's emission is fixed entirely by its temperature: total flux is sigma.T^4 and the spectral peak is at 2.898e-3/T. A 3000 K filament of 1 cm2 radiates 459 W with its peak at 966 nm - mostly infrared, which is why incandescent lamps waste so much energy as heat.

Formulas

Total emission

P = sigma A T^4

Spectral peak and photon energy

lambda(peak) = 2.8978e-3 / T; E = hc / lambda

Worked example

With the default values below, Blackbody Radiation Calculator returns Total Radiated Power of 459.3003. Change any input above and every figure here is recalculated in your browser.

Inputs used

Black body temperatureminimum 0 K
3,000 K
Surface areaminimum 0 m2
0.0001 m2

Results

Total Radiated Power
459.3003 W
Peak Emission Wavelength
965.92 nm
Photon Energy At The Peak
1.2836 eV
Emissive Power Per Unit Area
4,593,003.3 W/m2

Step by step

  1. 1Values used
  2. 2Total emission
  3. 3Spectral peak and photon energy
  4. 4Total Radiated Power= 459.3003 W
  5. 5Peak Emission Wavelength= 965.92 nm
  6. 6Photon Energy At The Peak= 1.2836 eV
  7. 7Emissive Power Per Unit Area= 4,593,003.3 W/m2

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why are incandescent bulbs so inefficient?

At 3000 K the peak sits in the near infrared, so only about 5-10% of the radiated power lands in the visible band.

Is anything a perfect black body?

Nothing exactly, but a cavity with a small hole comes very close, and stars are good approximations across most of their spectrum.

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